FIG. 1 illustrates a conventional semiconductor wafer processing system called the MRC "ECLIPS" system. The conventional system includes a load chamber 10 into which semiconductor wafers 20 are loaded. Next, a pump-down (roughing) cycle occurs, during which the loading chamber is evacuated via a fluid connection including roughing tube 50, open rough valve 60, and a mechanical pump (not shown) connected to rough valve 60. Then, the wafer 20 is transported via the transport system 40 to a high-vacuum chamber 30 for processing. Before loading the next wafer 20 into the load chamber 10, a vent cycle occurs. During the vent cycle, as depicted in FIG. 2, N.sub.2 gas is drawn into the load chamber 10 through open vent valve 70 in order to flush out load chamber 10.
During the pump-down cycle, aluminum particles thrown off the wafer 20 tend to be drawn into the roughing tube 50. When rough valve 60 is closed at the end of the pump-down cycle, a residual quantity of aluminum particles remains in the region A of the roughing tube 50. During the venting cycle, the N.sub.2 gas flow reintroduces the residual particles in region A of roughing tube 50 into the load chamber 10, which tends to contaminate subsequent wafer processing.
It is an object of this invention to reduce the accumulation of particles in a wafer loading chamber during successive roughing and venting cycles. It is a further object of this invention to reduce particle contamination in the loading chamber in a simple and inexpensive fashion.